Public Overrides Sub RemoveUsersFromRoles(ByVal usernames As String(), ByVal rolenames As String())

    For Each rolename As String In rolenames
        If rolename Is Nothing OrElse rolename = "" Then _
          Throw New ProviderException("Role name cannot be empty or null.")
        If Not RoleExists(rolename) Then _
          Throw New ProviderException("Role name not found.")
    Next

    For Each username As String In usernames
        If username Is Nothing OrElse username = "" Then _
          Throw New ProviderException("User name cannot be empty or null.")

        For Each rolename As String In rolenames
            If Not IsUserInRole(username, rolename) Then
                Throw New ProviderException("User is not in role.")
            End If
        Next
    Next

    Dim conn As OdbcConnection = New OdbcConnection(connectionString)
    Dim cmd As OdbcCommand = New OdbcCommand("DELETE FROM UsersInRoles " & _
                                             " WHERE Username = ? AND Rolename = ? AND ApplicationName = ?", conn)

    Dim userParm As OdbcParameter = cmd.Parameters.Add("@Username", OdbcType.VarChar, 255)
    Dim roleParm As OdbcParameter = cmd.Parameters.Add("@Rolename", OdbcType.VarChar, 255)
    cmd.Parameters.Add("@ApplicationName", OdbcType.VarChar, 255).Value = ApplicationName

    Try
        conn.Open()

        For Each username As String In usernames
            For Each rolename As String In rolenames
                userParm.Value = username
                roleParm.Value = rolename
                cmd.ExecuteNonQuery()
            Next
        Next
    Catch e As OdbcException
        ' Handle exception.
    Finally
        conn.Close()
    End Try
End Sub